#include <bits/stdc++.h>
using namespace std;
/*
John Watson
https://codeforces.com/profile/quangminh98
Mua Code nhu mua Florentino !!
*/
#define faster() ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define ll long long
const int maxn = 5e5 + 9;
const int segsize = 8 * maxn;
const ll oo = 1e18;
int n, t;
ll arr[maxn];
class SegmentTree
{
private:
struct Node
{
ll mn, mx;
Node(ll mn = 1e18, ll mx = -1e18) : mn(mn), mx(mx) {}
Node operator + (const Node& other)
{
Node res;
res.mn = min(mn, other.mn);
res.mx = max(mx, other.mx);
return res;
}
};
vector<Node> st;
int n;
void build(int head, int l, int r, ll *arr, int t)
{
if (l == r)
{
int idx = (l % n == 0 ? n : l % n);
int can = (l > n);
st[head] = Node(arr[idx] + can * t, arr[idx] + can * t);
return;
}
int mid = l + r >> 1;
build(2 * head, l, mid, arr, t);
build(2 * head + 1, mid + 1, r, arr, t);
st[head] = st[2 * head] + st[2 * head + 1];
}
Node query(int head, int l, int r, int u, int v)
{
if (l > v || r < u) return Node();
if (u <= l && r <= v) return st[head];
int mid = l + r >> 1;
return query(2 * head, l, mid, u, v) + query(2 * head + 1, mid + 1, r, u, v);
}
public:
SegmentTree(int n, ll *arr, int t) : n(n)
{
st.resize(segsize);
build(1, 1, 2 * n, arr, t);
}
pair<ll, ll> query(int u, int v) // min, max
{
Node ans = query(1, 1, 2 * n, u, v);
return {ans.mn, ans.mx};
}
};
signed main()
{
if (fopen("test.inp", "r"))
{
freopen("test.inp", "r", stdin);
freopen("test.out", "w", stdout);
}
faster();
cin >> n >> t;
for (int i = 1; i <= n; i++)
{
cin >> arr[i];
arr[i] %= t;
}
sort(arr + 1, arr + n + 1);
SegmentTree seg(n, arr, t);
ll res = oo;
for (int i = 1; i <= n + 1; i++)
{
pair<ll, ll> val = seg.query(i, i + n - 1);
ll mid = (val.first + val.second) / 2;
res = min(res, max(mid - val.first, val.second - mid));
}
cout << res << '\n';
return 0;
}
